Optical Glass Lenses Research Articles

High-efficiency ductile-mode grinding of optical glass lens by controlling tool feed rate and workpiece velocity

High-efficiency ductile-mode grinding of optical glass lens by controlling tool feed rate and workpiece velocity

3D shape measurement of a ground surface optical element using band-pass random patterns projection

For manufacturing a fine optical glass lens, it is important to obtain a 3D profile of a semi-finished product with a rough surface. We develop an active binocular 3D scanning setup to measure the 3D profile of a rough surface optical element. Two cameras simultaneously capture the band-pass binary random patterns which are projected on the target object. The highlight of this system is using the temporal correlation technique to determine the stereo correspondence between the pixels of the two cameras. The 3D point cloud can be reconstructed by the triangulation principle. Experiment results confirmed that this method effectively measures the rough surface of an optical element with sufficient accuracy.

Basic Study on High Efficiency Ultra-Precision Grinding of the Optical Glass Lens

The demand for large aperture lenses with high surface quality and form accuracy used for single-lens reflex cameras has been increasing. Generally, large aperture glass lenses are produced by ultra-precision grinding. Considering the increasing global competition, the grinding process has to be improved. However, highly efficient grinding causes worse surface quality, which leads to much polishing and ultimately results in lower form accuracy. Thus in this study, aiming at the realization of highly efficient and precise grinding of glass lenses, cross grinding of optical glass BK7 is carried out. As a first step of the study, the influence of grinding conditions on the surface quality is investigated experimentally.

非球面光学玻璃透镜的模压仿真研究

非球面光学玻璃透镜的模压仿真研究

J164033 Ni-Nb-Zr系におけるガラス成形金型用コーティング材料の探索

J164033 Ni-Nb-Zr系におけるガラス成形金型用コーティング材料の探索

A Monte-Carlo Approach for Modeling Glass Transition

Glass transition is an important factor in the thermo-forming of glass elements of precision geometries, such as optical glass lenses. Based on the theory of potential energy landscape, the master equations can be established to describe the slowdown of atomic motions in the glass transition range. However, the direct solution of these master equations is almost formidable as the hopping rates between basins vary in many orders of magnitude. To make use of the master equations in the finite element simulation of thermo-forming process, this article develops a Metropolis stochastic process by assuming that the basin-hopping probability at a given time interval depends only on the relative hopping rate between the target state and the present state. It was shown that with an infinitesimal time interval, this stochastic description degenerates to the master equations, and that with coarse time steps, the efficiency can be greatly improved with good accuracy. The advantage of this new method was demonstrated through the glass transition and thermo-forming simulations of selenium by integrating the stochastic process with the finite element method via the constitutive description of the variation of volume and viscosity with temperature and time.

Implementation of Glass Transition Physics in Glass Molding Simulation

Glass transition is the most important factor in the thermo-forming of glass elements of precise geometries such as optical glass lenses. Among many attempts to model the physics of glass transition, the Master equations based on the potential energy landscape (PEL) appear to be apropos. In this study, we used Monte-Carlo approach to approximately solve the master equations and further implement the Monte-Carlo method in the finite element simulation. We used Selenium as an example since its PEL has been quantified. Through the FEM simulations, it is found that the geometrical replication quality is the best when the forming is performed at the viscosity around 105~106Pa×s, that the residual stress developed in the cooling process can be minimized in the slow cooling process or through post-annealing process after moulding.

A Review of Neuroendoscopy and Potential Applications in Veterinary Medicine

The endoscope was first developed over 200 yr ago. Endoscopy has since been applied to many disciplines of medicine. Its application to the nervous system was initially slow and not widely accepted and mainly involved the biopsy of tumors and the treatment of hydrocephalus. Several reasons for neuroendoscopy's limited use include inadequate endoscope technology, high skill level required, the advent of the surgical microscope, and the development of other treatments such as ventricular shunting. Over the past 50 yr, improvements in optical glass lenses, fiber optics, and electrical circuitry has led to better equipment and a revival of neuroendoscopy. Neuroendoscopy is now used in many diseases in human medicine including hydrocephalus, neoplasia, and intracranial cysts. This review presents the history of neuroendoscopy, the equipment and technology used, and the possible translation of techniques currently used in human medicine to veterinary medicine.

Finite element prediction of the lens shape of moulded optical glass lenses

Glass moulding is a high-volume fabrication method suitable for producing optical components embedded in computer, communication, and consumer products, such as optical glass lenses in the camera modules of mobile phones. Despite the advantages of glass moulding, several difficulties encountered in the manufacturing process have yet to be overcome. The most critical issue is deviation between the formed lens and the original lens shape design. To overcome this obstacle, this study constructs a precise material model for optical glass with detailed thermal expansion, structural relaxation, and stress relaxation properties obtained from material experiments. This study also uses finite element analysis (FEA) to predict lens shape by incorporating this precise material model at 30°C above At (which is widely adopted by the industry). A subsequent verification moulding experiment demonstrates consistency between the predicted and experimental results. This study establishes and confirms a comprehensive FEA model for predicting the shape of moulded glass lenses.

ガラス成形金型用Ptフリーアモルファス合金のコンビナトリアル探索(M&P2009機械材料・材料加工部門技術講演会)

This paper describes the search for novel Pt-free thin film amorphous alloys for use as optical glass lens molds. Two Ni-Nb-Zr thin film libraries were fabricated by a combinatorial arc plasma deposition. From the results of an X-ray diffractmetry and energy dispersive X-ray fluorescence spectrometry, the amorphous composition region was decided in the Ni-Nb-Zr system. Five Ni-Nb-Zr thin film amorphous samples that exhibited non-crystallization over 100h heating at 723K were re-fabricated using a carousel type sputtering system. The samples were evaluated in terms of various properties: mechanical properties, anti-sticking properties to molten glass, and machinability, in order to find the most suitable composition for the optical glass lens molding die. As a result, Ni_<35>Nb_<40>Zr_<25> was found to be a suitable composition for a glass lens molding die material. This sample exhibited fracture stress of 1.71GPa, excellent anti-sticking properties to molten glass, and good machinability, which was improved by modifying the fabrication method.

Searching for Pt–Zr–Ni thin film amorphous alloys for optical glass lenses molding materials

This paper describes the search for Pt–Zr–Ni thin film amorphous alloys for use as optical glass lens molds. Six Pt–Zr–Ni thin film amorphous samples were fabricated by means of a carousel-type sputtering system. The samples were evaluated in terms of various properties: crystallization temperature ( T x ), hardness, coefficient of linear expansion, anti-sticking properties to molten glass, and machinability, in order to find the most suitable composition for the optical glass lens mold. As a result, Pt 50 Zr 36 Ni 14 was found to be a suitable composition for a new molding material. This sample exhibited a T x of 985 K, a hardness of 8.2 GPa, a similar the coefficient of linear expansion of glass material, excellent anti-sticking properties to molten glass, and good machinability, which was improved by modifying the fabrication method. Finally, we fabricated a glass lens mold with diffraction gratings from Pt 50 Zr 36 Ni 14 amorphous alloy.

순차이송방식 GMP 공정에서 공정변수가 유리렌즈 성형성에 미치는 영향

Remarkable progress had been made in both technology and production of optical elements including aspheric lens. In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. Against such a background, the high-precision optical GMP process was developed with an eye on mass production of precision optical glass pasts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as for cameras, video cameras, aspheric lenses for optical items. In this study, Design Of Experiment(Taguchi method) was adopted to find a tendency of molding conditions that influence formability. Three main factors for molding conditions were selected based on pressure at pressing stage and temperature, pressure at cooling stage. Also, the DOE was carried out and the interference patterns were measured to evaluate the formability of GMP process. From the results, it was found that the cooling pressure is the most sensitive parameter for progressive GMP process.

Characterization of the Pt-Hf-Zr-Ni Thin Film Amorphous Alloys for Precise Optical Glass Lens Mold

We researched the characteristics of the Pt-Hf-Zr-Ni thin film amorphous alloys for precise optical glass lens mold. The five Pt-Hf-Zr-Ni thin film amorphous alloys having various alloy composition were prepared. Desired characteristics for the glass lens mold were researched. Thus, the Pt51Hf20Zr17Ni12 sample was found as the candidate material for the glass lens mold. This sample showed the crystallization temperature of 994 K, the fractured stress of 1.01 GPa and anti-sticking properties to molten glass. However, since the Pt51Hf20Zr17Ni12 sample exhibited insufficient oxidation resistance, it is necessary to inhibit oxidation with protective coating in order to apply this sample to glass lens mold. Moreover, the Pt51Hf20Zr17Ni12 sample fabricated using alloy target could be cut to taperd shape by the single crystal diamond tools without tool wear.

An Experimental Study on Flow Characteristics of PBK-40 for Glass Molding Press Simulation

Remarkable progress had been made in both technology and production of optical elements including aspheric lens. Especially, requirements for machining glass materials have been increasing in terms of limitation on using environment, flexibility of material selection and surface accuracy. In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. Against such a background, the high-precision optical GMP process was developed with an eye on mass production of precision optical glass pasts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as for cameras, video cameras, aspheric lenses for laser pickup, f-θ lens for laser printer and prism, and fine glass parts including diffraction grating and V-grooved base. Generally, GMP process can be classified into batch and progressive type. In these types, because progressive type has many merits in that productivity is higher and repair/retouch of mold is easier than batch type, progressive GMP process is mainly used to produce aspheric glass lenses these days. In this paper, as a fundamental study to develop the multi-cavity mold for higher productivity of progressive GMP process used in fabrication of aspheric glass lens, compression tests for K-PBK40, which is the material of aspheric glass lens, were conducted at high temperature. As a result, flow characteristics of K-PBK40 were obtained for aspheric glass lens press simulation.

Machinability in Precision Grinding of Aspheric Optical Lens with Diamond Wheel

In order to do the precision grinding of optical aspheric lens, it is essential to achieve high quality surface roughness. Experiments show that the contacting area between the wheel and workpiece in a grinding process is critical to influence the surface roughness for a fine grit size resin bonded wheel. The precision grinding are performed with BK7 optical lens. This paper deals with the grinding of an aspheric surface optical lens by diamond wheel. This study also compares each machining parameter (work spindle speed, wheel spindle speed, feedrate, etc.) in rough grinding, fine grinding and polishing on the aspheric lens. In this study, several experiments were carried out BK7 optical glass lens by using vitrified, metal, resin bond diamond wheel and the polisher of urethane ball was used to remove the tool marks with an ultra-precision in-line grinding system. It was found that machining parameters significantly influence the surface roughness of aspheric optical lens.

A Study on the Aspheric Glass tens Forming Analysis in the Progressive GMP Process

In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric glass lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical glass molding pressing (GMP) process was developed with an eye to mass production of precision optical glass parts by molding press. In this paper, as a fundamental research to develop the multi-cavity mold for higher productivity of a progressive GMP process used in the fabrication of an aspheric glass lens, an aspheric glass lens forming simulation was carried out.

Prediction of birefringence distribution for optical glass lens

Abstract Based on the viscoelastic theory, simulations were carried out on glass-lens forming processes. In addition, the birefringence distribution was calculated by stress-optic relation. First, to verify this viscoelastic simulation, FEM analysis was performed with the same material properties and process conditions used in the Bruckner's experiment. The result of the analysis was compared with Nadai's and Bruckner's results. The simulation results were in good agreement with the deformation and birefringence distribution in the experimental results. Finally, the FEM simulation technique was applied to actual LD-lens. The simulation was performed for each different cooling rate and the results were compared to each other in terms of birefringence. To investigate the effect of initial preform shape to optical property, a simulation was performed by using the new-proposed-shape-preform and the results were compared to the present shape in terms of birefringence.

Combinatorial Searching for Pt-Zr-Ni Thin Film Amorphous Alloys for Glass Lens Mold

AbstractRecently, the materials of functional optical glass lens mold have been studied. We had searched for the novel amorphous alloy having high crystallization temperature Tx using combinatorial arc plasma deposition (CAPD). In the previous work, Ru-based and Pt-based alloys were investigated. Although these amorphous alloys had high Tx of more than 973 K, they did not show good machinability. In this work, in order to progress machinability of amorphous samples, the various properties of the Pt-Zr-Ni thin film amorphous alloys were investigated. The properties of desired sample were as follows: (1) Tx exceeds 923K. (2) sf exceeds 2.0GPa. (3) Non-sticking characteristics with melting glass. (4) Good machinability.As the process of searching for amorphous alloys, 3267 samples were deposited by CAPD. The phase and composition of the CAPD samples with thickness more than 500nm were evaluated. Thickness of the CAPD samples was measured by a white-light interferometer. Compositions were measured by an energy dispersive X-ray fluorescence spectrometer. Phases were identified by an X-ray diffractmeter. From these results, 312 amorphous compositions were found. The period of searching for amorphous composition was only about twenty days. This shows the effectiveness of CAPD.Tx and fracture stress Ðf of the sputter-deposited amorphous samples having the same composition as amorphous CAPD samples were measured because CAPD samples were too small to evaluate thermal and mechanical properties. Tx was measured by differential scanning calorimeter. sf was measured by tensile tests using a thermo-mechanical analyzer.At first, in order to investigate the effect of Pt-content on Tx, the PtxZr (90-x)Ni10 samples were fabricated by the sputter. Pt-content was ranged from 20 to 50 at.%. Tx increased with increasing Pt-content, and the Pt51Zr39Ni10 sample showed the highest Tx of 939K. The sample has needs to show Pt-rich composition to show Tx of more than 923K. However, sf of all sample showed less than 2GPa.Subsequently, in order to search for Pt-rich sample having high sf, the properties of the Pt50Zr(50-x)Nix sample were investigated. Ni-content was ranged from 5 to 15 at.%. As the results, Tx increasing with increasing Ni-content. The Pt50Zr36Ni14 sample showed the highest Tx of 985 K and Ðf of 2.12 GPa.Sticking characteristics of the Pt50Zr36Ni14 sample with melting glass were measured. Melting glass was felled in drops on the samples, and then droplet was removed without adhering to the sample. Machinability of the Pt50Zr36Ni14 sample was evaluated by cutting tests using diamond tools. Surface roughness of this sample worked was several nanometers. This result indicated that the Pt50Zr36Ni14 sample showed good machinability. From these results, it is considered that the Pt50Zr36Ni14 sample is suitable for the materials for glass lens mold.

The Nondestructive Evaluation Method for the Optical Glass Lens by Resonant Ultrasound Spectroscopy

In this research, we proposed nondestructive evaluation method of a flaw in an optical glass lens by resonant ultrasound spectroscopy (RUS). An optical glass lens is used for improving signal coupling between fibers, emitters and detectors. The shape of optical glass lens is an aspherical lens with 3mm in length and 6.35 mm in diameter. For nondestructive evaluation of an aspherical lens, we made of the measuring system by RUS. For flaw evaluation by the RUS to verify the data obtained from the experiment, we carried out simulation by explicit finite elements method, and compared the experimental results with simulation results. Also, we compared the resonant frequencies of specimens with some defect with those of acceptable specimens. The histogram drawn from these data and the available resonance mode surveyed were used to classify the acceptable specimens in the plant.

Development of a novel binderless diamond grinding wheel for machining IC chips for failure analysis

The objective of this research is to machine the silicon die of an IC chip and the surrounding chip packaging. The silicon die had to be reduced from a thickness of 85 μm to about 50 μm by a machining technique such that not a single transistor of the 40 million under the die is destroyed and at the same the die presents a mirror finish for examination on a back emission infra red microscope. The chip packaging had to be machined such that the six layers of power conduits in the form of copper traces and the dielectric (insulator) between them could be studied at low magnification for discontinuity. Initially electroplated diamond grinding pins were used for the die that was successful but it left undesirable tracks behind that remained even after polishing. These pins were not ideal for the soft but tough chip packaging. A new binderless diamond grinding wheel was developed that had a width equal to that of the IC chip die and also that of the width of the chip packaging with considerable success. This new wheel was also used to machine plano silicon and optical glass lenses successfully.